I. Field of the Invention
The present invention relates to compositions and methods for controlling mastitis in animals. More particularly, a modified polysaccharide based composition forms a barrier film that is useful in protecting the teats of dairy animals from microbial infections of the milk channels. The barrier efficacy may be further enhanced by inclusion of germicidal or antimicrobial agents.
II. Description of the Related Art
One major cause of economic loss for dairy farmers is the incidence of mastitis in cows or dairy animals. Overall annual economic losses due to mastitis approximate $185 per dairy animal. This totals to approximately $1.7 billion annually for the entire United States market.
Mastitis is typically caused by infection of the milk ducts by microorganisms. Severe cases of mastitis may cause death of the dairy animals. Milder cases of mastitis are more common, and may result in loss of milk production together with an increased cost of veterinary care for the dairy farmer.
Dairy farmers have traditionally taken two approaches to prevent the cows from contracting mastitis. Antimicrobial compositions may be used to reduce the risk of infection. One measure employs germicidal agents to kill the microbes. The other approach uses a persistent film-forming composition that is applied to the bovine teats as a barrier to block the microbes from entering the milk ducts.
Despite intensive research and testing for an ideal composition that can effectively protect the animals from mastitis, many problems persist. Although many compositions can form a layer of film over the teat skin, the film tends to crack during drying, leaving some areas of teat skin unprotected. Some compositions form a layer of film over the skin that is too easily washed off when in contact with dung, mud or water. Other materials cannot be removed easily enough, and may be a source of contamination that complicates the milking and milk purification process. Moreover, some film-forming components are incompatible with the germicide and other ingredients essential for formulations, resulting in a reduced potency of the germicide. It is difficult to formulate a protective film that is continuous, uniform, non-brittle, persists 8-12 hours on the teat between milkings, mild on skin, easily removed by cleaning prior to milking and is non dripping when applied.
U.S. Pat. No. 5,063,249 issued to Andrews describes a teat dip containing dodecylaminolkylamine derivatives, an emollient and Poly(N-VinylPyrrolidone) (or “PVP”) as a film-forming ingredient. However, the teat dip described in this patent is highly fluid and, consequently, is less likely to adhere to the teat skin as the formulation is not able to vertically cling onto teats with sufficient strength to form a long-lasting protective film. Furthermore, due to low viscosity and dripping, the product does not form a persistent protective film.
Another type of barrier utilizes cellulose as a barrier-forming agent. U.S. Pat. No. 5,776,479 issued to Pallos et. al. discloses a germicidal teat dip composition that contains a film-forming ingredient selected from the group consisting of hydroxyethylcellulose, methylhydroxypropylcellulose and ethylhydroxyethylcellulose. The composition also includes a germicidal agent, such as iodine, which complexed with a nonionic surfactant and water to provide a solution having a viscosity of from about 50 to 1000 cPs. After being applied to the teats of agricultural animals, the liquid dries to form a continuous barrier film.
EP 896,521 B1 describes a barrier-forming mixture that uses a longer chain polysaccharide derivative, such as methylcellulose or hydroxyethylcellulose that is present in an amount ranging from 10% to 20% of the composition by weight. The efficacy of this polysaccharide material is enhanced by the use of a low molecular weight saccharide material that may be, for example, a monosaccharide or disaccharide and may include hydrolyzed starches, such as maltodextrin. Although the polysaccharide material and the saccharide material are not exceptionally effective alone, a synergistic effect is achieved when the materials are used in combination such that the low molecular weight synergistic saccharide is present in an amount ranging from 2% to 10% of the composition by weight, or roughly 20% to 50% of the amount of polysaccharide.
The use of polysaccharide based cellulose and cellulose derivatives in teat dip compositions present a number of problems. The solutions tend to drip after application to the teats, and a certain amount of product is wasted. The dripping of the applied solutions also results in a thinner barrier film than is not ideal for use on dairy animals. It is difficult to formulate quick-drying compositions because cellulose is relatively insoluble in commonly used volatile solvents, such as short chain alcohols.
U.S. Pat. No. 6,030,633 issued to Hemling et al. describes a film-forming composition to protect dairy animals from contracting mastitis during the dry period of the dairy animals. The composition includes a film-forming component such as a mixture of polyether, polyurethane and benzoin gum, which is dispersed in a compatible carrier and forms an elastic barrier film when applied on the skin. The composition also contains a small amount of nitrocellulose, in order to enhance the adherence of the film to the skin. The composition further includes a germicide to kill microorganisms that break the physical barrier.
Although polysaccharides such as hydroxypropyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose and non-polysaccharides such as polyvinylpyrrolidone, etc. are typically used in combination with film barrier agents in aqueous film coating, when used alone they often produce inferior film on teats. Moreover, these ingredients are expensive. Although, polysaccharides may assist the formation of high quality films when used in combination with other film forming agents, formulators are constantly looking for more efficient, better alternatives to enhance coatings or lower overall cost of the coatings.
Much progress has been made in preventing the incidence of mastitis, but there remains a need for a composition that is not only germicidically effective but also forms a long-lasting persistent, continuous, uniform film as a physical barrier between the animal skin and microorganisms in the environment. A need also exists for such films to be easily removed so as not to contaminate milk, while also lasting long enough to protect from bacteria in between milking. The duration of film coverage is normally 8 to 12 hours, but may occasionally be as long as 24 hours.